Vehicle exhaust heat recovery system and method of managing exhaust heat

Abstract

An exhaust heat recovery system (EHRS) for a vehicle is operable to direct exhaust heat to a vehicle transmission under certain operating conditions. In some embodiments, the EHRS may also direct exhaust heat to a heater for vehicle passenger compartment. Preferably, the EHRS is controllable to manage available exhaust heat according to vehicle operating conditions, by prioritizing the heat flow among the engine, the transmission, and the vehicle heater. The EHRS may also operate in a bypass mode during which exhaust heat is not directed to the engine, the transmission or the vehicle heater. A method of managing exhaust heat recovery on a vehicle having an EHRS is also provided.

Description

TECHNICAL FIELD[0001]The invention relates to an exhaust heat recovery system for a vehicle, and a method of managing exhaust heat.BACKGROUND OF THE INVENTION[0002]Rapid warm-up of engine fluid, engine oil, and transmission fluid is important to fuel economy during a cold start (i.e., when the vehicle has not been running and the engine and transmission are relatively cold). Engine warm-up is especially challenging for diesel and hybrid applications, as less fuel is burned. Adequate passenger compartment heater performance is also necessary for passenger comfort. Powering the heater using a motor / generator on a hybrid vehicle can negatively impact fuel economy.SUMMARY OF THE INVENTION[0003]An exhaust heat recovery system (EHRS) for a vehicle is provided that is operable to direct exhaust heat to a vehicle transmission under certain operating conditions. In some embodiments, the EHRS may also direct exhaust heat to a heater for vehicle passenger compartment. Preferably, the EHRS is c...

AI Technical Summary

Benefits of technology

[0009]Still further, the valve controllable to permit exhaust heat flow to the transmission heat exchanger (referred to as the transmission valve) may be positioned to permit fluid communication between the engine and the transmission heat exchanger if the engine load is above a predetermined threshold engine load, engine speed is above a predetermined threshold engine speed, and / or transmission temperature is above a predetermined maximum transmission temperature. The fluid thus communicated does not pass through the exhaust heat recovery device between the engine and the transmission heat exchanger, as it is fluid cooled by the engine cooling system that is then used to cool the transmission. Under these operating conditions, the exhaust heat is not directed from the exhaust heat recovery device to the conduits, although some minimal amount of heat may be transferred from the exhaust system to the conduits simply due to proximity of the components. By cooling the transmission under such engine loading, engine speed, and / or transmission temperatures, transmission durability and fuel economy may be improved.

Problems solved by technology

Engine warm-up is especially challenging for diesel and hybrid applications, as less fuel is burned.

Powering the heater using a motor / generator on a hybrid vehicle can negatively impact fuel economy.

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